1. Field of the Invention
The invention relates to an auxiliary apparatus for controlling electrically operated functional devices, such as solenoid valves, designed to replace a main control unit such as, for example, an automatic controller, should it fail, and more particularly to an auxiliary apparatus for controlling valves of a gas delivery facility also known as a gas cabinet.
2. Description of the Related Art
The fabrication of microelectronic circuits requires the use of various gases called "working" gases such as, for example Cl.sub.2, NH.sub.3, HCl, HBr, NF.sub.3, WF.sub.6, etc., which gases are for the most part regarded as being dangerous to humans because of their toxicity and/or their inflammability.
These gases are taken to stations where they are used, such as stations for the fabrication of microelectronic circuits, via a gas cabinet.
Because of the toxicity of the gases employed, the safe control of the operation of such a supply cabinet is an absolute priority. This is why such cabinets are generally equipped with an automatic controller for controlling and operating the various valves placed in the cabinet.
For economic reasons, it is necessary, should the automatic controller fail, to be able to continue to operate the valves.
For this purpose, an auxiliary apparatus for controlling solenoid valves, which is designed to replace the automatic controller and be plugged into the latter's connection terminals that are provided for this purpose, is known.
This apparatus comprises, for each solenoid valve, a manually operated switch interposed between a line for delivering an electric control potential, this line being intended to be connected to an associated supply terminal of the automatic controller, and an associated line for transmitting the electric control potential to a predetermined solenoid valve.
This apparatus has the drawback that the operator may inadvertently set one or more switches in a closed position when connecting the apparatus to the automatic controller so that the valves associated with these switches open adventitiously, which in turn may cause considerable damage to equipment or even to personnel.